Fan blade



Sept. 7, 1937.

FAN BLADE Filed Sept 3, 1935 2 Sheets-Sheet l I INVENTOR. I l Ge'az-qeSou/eg ATTORNEYS G. w. SOULES 2,092,030 Q Sept. 7, 1937. w. SQULES 2,092,030

FAN BLADE Filed Sept.

3, 1935 2 Sheets-Sheet 2 INVENTOR ATTORNEYS Patented Sept. 7, 1937 FAN BLADE George W. Soules, Detroit, Mich. Application September 3, 1935, Serial No. 38,859

2 Claims;

The present invention pertains to fans of the type particularly adapted for providing an air current in ventilating apparatus, heating apparatus, cooling systems of various types and innumerable surroundings where movement of air is desirable.

Fans operating at comparatively high speeds are known to have the undesirable characteristic of setting up considerable noise, most of this noise being the result of the boundary layer of air tearing away from the rear surface of the blade and to the formation of a partial vacuum behind the blades which other free air rushes in to fill. The present invention has as its primary object to prevent as nearly as possible tearing away of the boundary layer of air adjacent to the fan blades and to provide for a more uniform and silent flow of air into the low pressure zone behind the blades.

During operation of fans at high speed air has a tendency to move radially outward and to spill over the tip of the blade into the partial vacuum behind the blade. The present invention has asanother object to provide a-blade formation which materially reduces the tip loss and at the same time provides a sharply defined air stream.

Another object of the present invention is to provide a fan blade wherein a novel combination of cambers, pitch angles, concavities, blade contour and weight distribution result in an increase in the air delivered for a given power input. It is well known in connection with the fans that the amount of air delivered is directly proportional to the speed of movement of the blades,

that is, when the speed of the fan is doubled the volume of air delivered is doubled and'the pressure varies as the square of the speed so that doubling the speed increases the pressure four times. However. the power required to run the fan varies as the cube of the speed so that when the speed of the fan is doubled it requires eight times as much power to operate it, and therefore it may be seen that even a slight increase in 45 efficiency in the fan blade results inan appreciable reduction in power consumption.

With the above and other ends in view the invention is more fully disclosed with reference to the accompanying drawings in which 50 Figure 1 is a front elevation;

Fig. 2 is a side elevation;

Fig, 31s a plan, and

Figs. 4, 5, 6, '7 and 8 are sections taken respec- 5 tlvely on the lines 4-4, 5-5, 6-6, 1 -1 and 8-8 5 of Fig. 1.

Like characters of reference are employed throughout to designate corresponding parts.

As illustrated the present fan comprises a hub I having an axial bore 2 for the reception of a motor shaft to provide a support therefor and means for receiving power for the purpose of rotating the same. As is more clearly shown in a Fig. 1 the leading edge 3 of the blade is concave and it extends forwardly in the direction of travel of the blade. The upper portion of the line 8-4 10 extends radially and perpendicular to the axis of the hub I and the leading edge 3 diverges outwardly from this portion of the line 8. The trailing edge a of the blade is convex and it diverges outwardly with respect to the leading edge 3 so 15 as to provide the zone of greatest width of the blade, which is generally designated by the numeral 5, at a point considerably nearer the tip '6 of the blade than the hub.

Referring now to Fig. 8 it will be seen that the 20 force face or work face 1 of each blade is concaved, the concaved surface extending continuously from the tip 6 to its point of union with the hub l indicated. at 8. It is also to be noted from the showing in Fig. 8 that the thickness of 25 the blade gradually tapers from a point of union with the hub to its tip 6 and that the rear face 9 constitutes a convex surface extending continuously from the tip 6 to its point of union with the hub.

Referring to Fig. 7 which is a View taken substantially along the line 1-1 of Fig. 1 at right angles to the line 8-8, it will be seen that the portion at the plane here illustrated constitutes the thickest part of the blade. The force face 35 at this particular part has a pitch angle represented by the line A-A. The line B-B which is common to Figs, 4 to 7 inclusive represents the plane of rotation of the blade. The force face at this particular portion is convex as indicated by 40 the numeral Ill and the rear face is also convex as indicated by the numeral II and the section corresponds to a streamlined body.

Referring to Fig. 6 which is a section taken at a point more remote from the axis than the view Fig. '7, it will be seen that the work face Illa at the plane here illustrated is concave and the rear face I la is convex and that the part of smallest thickness is at the trailing edge 4. In this figure the line C-C represents the pitch angle of the work face and it will be noticed upon comparison with Fig. '7 that the pitch angle is reduced. It will also be noted that the cross sectional thickness of the blade at this point is thinner than at thepoint illustrated in Fig. '7.

face is also concave called airplane propeller type In Fig. 5 the width of the blade from the leading edge 3 to the trailing edge 4 is considerably increased over the width of the same at the point shown in Fig. 6, thus illustrating that the width of the blade progressively increases as it extends outwardly from the axis. At this point the work as designated at I 011 and the rear face is convex as at l lb. It will be noted, however, that the convex arc llb is considerably flatter than the corresponding arc Ila in Fig. 6 and that as the width of the blade increases its thickness decreases, this being readily apparent upon comparison of the thickness of the blade at the point shown in Fig. 6 with the point shown in Fig. 5.

Fig. 4 illustrates a section of the blade at the width, the distance between tance shown in Fig. 5, and it will be noted that the thickness of the blade at the point shown in Fig. 4 is less than that shown in Fig. 5. The work surface Illa is concave plane and the rear surface H0 is convex, the arc that the pitch angle decreases progressively as the blade extends outwardly from the hub.

It has been found from actual tests that the blade having diverging leading and trailing edges curving forwardly into the direction of movement of the blade and providing the portion of greatest width considerably nearer the tip of the blade than the hub, in combination with the concave formation of the work surface in the plane shown in Fig. 8 and the gradually changing work surface which starts with a convex surface adjacent to the hub and gradually changes into a concave surface as it extends outwardly toward the tip, when viewed transversely to the plane ofFig. 8, results in greater efficiency than can be obtained by use of the conventional sofan blade under equal static pressure conditions for a given power input. It has also been found that this contour in combination with the cambers, pitch angles, weight distribution and combination of convex and concave surfaces provides for much quieter operation and that it results in a sharply defined air stream.

Although a specific embodiment of the invention has been illustrated and described it will be understood that various changes may be made within the scope of the appended claims without departing from the spirit of the invention and such changes are contemplated.

What I claim is:-

1. A fan .blade having a hub and a rounded tip, said blade having leading and trailing edges and work'and rear faces, said leading and trailing edges diverging outwardly from said hub and being united by said rounded tip, said leading edge being concave to thereby position therounded tip forwardly in the direction of travel greatest convexity immediately adjacent to said hub and the portion of least convexity adjacent to said tip, the convexity of said rear face being gradually varied between said hub and tip, said work face being concave throughout a substantial portion of its length, and said blade having a gradually varying pitch angle which decreases as the blade extends outwardly from said hub, the arrangement being such that the portion of the rear face having the least convexity is disposed in the part of the blade having the smallest pitch angle.

2. A fan blade having a hub and a rounded tip, said blade having leading and trailing edges and work and rear faces, said leading and trailing edges diverging outwardly from said hub and being united by said rounded tip, said leading and trailing edges and rounded tip being so formed that the widest part of the blade is immediately adjacent the tip zone, said leading edge being concave and said trailing edge being convex throughout its entirelength, said rear face being convex and of varying convexity with the portion of greatest convexity immediately adjacent to said hub and the portion of least convexity adjacent to said tip, the convexity of said rear face being gradually varied between said hub and tip. said work face being concave throughout a substantial portion of its length, said work face having a convex portion immediately adjacent to said hub merging into the concave portion thereof, the concavity of said work face being varied from the convex zone to the tip in such manner as to provide a zone with the least concavity directly opposite to the rear face portion having the least convexity, and said blade having a gradually varying pitch angle which decreases as the blade extends outwardly from said hub, the arrangement being such that the portion of the rear face having the least convexity is disposed in the part of the blade having the smallest pitch angle.

GEORGE W. SOULES. 

